A Chilling Reality: The Expensive and Uncomfortable State of Indoor Climate

by Shaun May, EIT

This article is part of Wood Harbinger’s newsletter series.

Excessive indoor cooling is costing us all a lot of money, so much money it sends chills down my back just thinking about it… Or, is that just the A/C? Multiple studies and articles have discussed the negative effects that cold offices have on employee productivity. A survey of employees in the United Kingdom revealed that nearly one third of workers report lost productivity due to uncomfortable office temperatures, “potentially costing the UK economy more than £13 billion [$18.5 billion] annually.” The U.S. General Services Administration surveyed more than 6,000 federal workers and concluded that “overcool indoor air in summer is uncomfortable.” People should not be cold in their office when it is hot outside, yet clearly this issue permeates our built environment.

Why are buildings operated at such chilly temperatures? How do we get the indoor climate back under our control and suited for everyone? How much money can be saved by not overcooling indoor spaces? As summer finally comes to Puget Sound, this issue is “heating up,” so let’s speak frankly.

Who Designed this Icebox?!

Engineers design Heating, Ventilation and Air Conditioning (HVAC) systems to optimize occupant comfort, business productivity, and building energy efficiency. We design to fulfill the building Owner’s standards. We also design to meet building energy code criteria; energy codes are defined at a state level and sometimes to a more localized jurisdiction (e.g., the City of Seattle has defined the Seattle Energy Code). We also utilize design standards and guidelines developed by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE).

If occupant comfort is part of the design, then why are these sadistic engineers making it so uncomfortable, you may ask. Let’s look at some of the factors that must be considered before you grab your pitchforks and torches.

Designed for the Man in the Suit

Typically, conditioned indoor space temperatures are set between 68 to 72°F. ASHRAE Standard 55 specifies conditions for acceptable thermal environments and identifies six primary factors that must be addressed when defining conditions for thermal comfort:

  1. Metabolic rate
  2. Clothing insulation
  3. Air temperature
  4. Radiant temperature
  5. Air speed
  6. Humidity

Let’s break it down:

In the temperate Pacific Northwest, humidity is rarely a concern for general use in occupied spaces, such as offices, and isn’t controlled by mechanical systems. In the more humid climates of the South or the Northeast, engineers include dedicated dehumidification systems in their designs to address this factor. Air speed is driven by building ventilation requirements and should be imperceptible to occupants, if the ventilation systems are properly designed and balanced. Radiant temperature involves the heat emitted and/or absorbed by objects in the space: computers, people, surfaces, and so on. Again, with the proper information about the types and volume of objects in the space (occupant density, number of workstations, etc.), this can be addressed through good mechanical design and should be imperceptible to the occupant. There can always be an exception, however. We can all remember an experience of being in an over-filled conference room because it was the only one available for that last-minute, all-hands-on-deck meeting, and you grew acutely aware of your co-workers’ radiant heat when the room became stifling….

When air speed, humidity, and radiant temperature are properly addressed, air temperature becomes the most crucial factor in achieving occupant thermal comfort. However, the more fluid, human-influenced factors, metabolic rate and clothing insulation, come into play in how air temperature is perceived. As we take a closer look at these thermal comfort factors, keep in mind that engineers tend to design conservatively in order to handle the worst case scenarios.

Metabolic rate varies from person to person and is based on activity level; the more activity, the higher your metabolic rate. In an office environment, people are mostly sedentary at their desks, so an average resting metabolic rate is factored in. Men tend to have higher resting metabolic rates than women and so they feel warmer. Now consider clothing insulation. In many commercial and professional office spaces, business professional attire remains the norm.

So, in designing for the worst case, air temperatures are typically designed to keep the man in the suit comfortable. This scenario is the foundation of the standard 68 to 72°F temperature range defined for office thermal comfort that engineers use as the basis for HVAC system design.

Unless an Owner’s standards specify another range, people who are not men in suits may find their office too cold for them. With women comprising nearly half of the U.S. labor force and dress codes evolving in some companies, the potential exists for a lot of uncomfortable occupants. The UK and U.S. GSA surveys lend support to this outcome.

Freeze! Time to call the fashion police!

This leads us into the topic of building operations and the occupants’ role. Corporate culture just doesn’t seem to adapt with the changing weather of the seasons. Whether it is deep winter or sweltering summer, tradition dictates similar attire in the workplace: suit up!

Thus, we establish a vicious cycle of overcooling our over-clothed workforce, over-consuming energy to operate the AC systems, and overlooking the negative effects on productivity.

I’m so over it! Can this rigid refrigeration cycle be overturned?

Natural Rather than Forced

The targeted indoor air temperature relates to the thermal “deadband”—the temperature range in which both mechanical heating and cooling are off. The typical 68°-72°F temperature range for office spaces is a very tight range to maintain. This results in near-continuous workday operation of the mechanical heating and cooling systems during the colder winter temperatures and warmer summer temperatures.

The systems are potentially heating from 6am to 10am to bring the building up to temperature, then cooling from 10:30am to 6pm. That morning changeover is verging on the edge of “simultaneous heating and cooling,” which is not only against building energy codes, it is like an icepick in an engineer’s heart. Oh, the inefficiency!

Thankfully, a new wave of innovative ideas are flowing out of sustainability-minded developers and designers. One of these is an oldie but goodie: natural ventilation. By providing natural rather than forced air ventilation and by expanding the thermostat “deadband,” we can save energy. In other words, we can maximize the time that fans, heating, and cooling (all mechanical systems) are off.

I heard this concept coined as “design for off,” at the AIA Net-Zero Energy Conference that my colleague Matt Woo and I attended in Seattle last year. Natural ventilation was a common element in the commercial built environment decades ago, but it has not been the norm more broadly.

Adaptive Behavior

Let us back up and take a common sense approach. When it’s hot outside, say 90°F, if I walk into an 80°F indoor space, it feels nice and cool. I am relieved and feel sheltered from the oppressive heat outdoors. If I walk into a 70°F space, brrrrrr! This (relative) seasonal psychological effect needs to be taken into account. For this reason, increasing the top of the temperature “deadband” to 78°F could be a viable option to increase occupant comfort and save energy.

“78°F?! That is too hot for indoor spaces!” Maybe, if you’re wearing a full suit. But if you’re wearing lightweight slacks and a short sleeve shirt, or a skirt and blouse, or (gasp) formal shorts, you may well feel pretty comfortable, which leads to a conversation about how company dress codes might adapt to accommodate a changing indoor environment.

“Business casual” has gained traction over the years and continues to evolve. A recent article in The Atlantic asked, “What is “casual,” actually? We still wonder. Office shorts—yea or nay? Flip-flops? Yoga pants? When Mark Zuckerberg gives his keynote presentations in a t-shirt and jeans, what does that mean for the rest of us? It is, for the moment, unclear.

Cash Considerations

Are formal shorts, short-sleeves, and other casual clothing options okay for your business? For companies who are willing to consider this question, here’s another question to consider in tandem. “How much money can be saved by throttling back the A/C?” The short answer to that question is hundreds of dollars per month.

The GSA study determined they could save 18.7 million kWh per year by adjusting the ambient indoor temperature of federal offices to between 74°F-78°F. With Washington State’s relatively inexpensive energy ($0.08/kWh), that would be a $1.5 million savings, for example. The savings only goes up if you factor in the higher prices of energy around the country.

Here’s a quick matrix of energy savings, based on a typical office environment makeup outlined in ASHRAE Standards:

Office Cooling Savings in Peak Summer

Indoor Air Temperature Setpoint Cooling Cost Savings from Baseline per month
72°F $0
74°F $650
76°F $1,300
78°F $1,950

Calculation notes:

  • 50 occupants
  • 10,000 square foot office space
  • Seattle August cooling design outside air temperature of 82°F (ASHRAE Handbook)
  • $0.08/kWh, Seattle July/August cooling degree-hours base 80°F (CDH80) = 220 hr./mo., 50% duty cycle

Note that even adjusting the setpoint by 2°F can save hundreds of dollars per month in average office spaces. Therefore, incremental change is recommended. It is definitely low risk, high reward.

Shedding Extra Layers

Energy savings from cooling system adjustments are only the tip of the iceberg. Consider the domino effect that this change could initiate. Productivity would likely increase for those who were previously uncomfortable in their over-cooled office interiors. Those who were the coldest can now store their Snuggies and turn off those space heaters, thank heavens.[1] Commuters would be empowered to travel lighter without needing to carry with them an office-specific wardrobe; this could be huge because it would make alternative transportation options, like mass transit or carpooling, more viable options.

Stewardship

Sustainability is about achieving harmony with nature; let’s stop fighting the weather. There are incremental steps we can take to improve the work environment and realign indoor and outdoor environments. Relax temperature setpoints, relax attire requirements, and watch the workforce come to life. Adapting our conditioned environments to the season, and clothing for both simultaneously, are small steps to design and operate a built environment that harmonizes with the natural one. In doing so, we may reconnect with, and therefore become better stewards of, the world in which we live.

 

 

[1] Space heaters are a prime example of simultaneous heating and cooling. However, since the individual use of space heaters isn’t part of the building’s intentional design and operation, they slide under the energy code radar. Cooling down a whole building, only to heat small pocket spaces back up with energy-guzzling space heaters… That could crush any designers’ dreams.

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